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In order to protect high-field superconducting magnets during a quench with rapidly rising hot spot temperatures, it is important to have a quantitative understanding of quench behaviors of superconducting wires at high magnetic fields. In this article, we developed a two-dimensional numerical model of quench initiation and propagation in Bi2Sr2CaCu2Ox/Ag/Ag alloy (Bi2212) multifilamentary composite round wires with the H-formulation and the heat conduction equation. The results show that the minimum quench energy (MQE) of Bi2212 round wires decreases with increasing magnetic field and closely relates to the current sharing temperature (Tcs). For a constant ratio of the transport current to the critical current (It/Ic), the normal zone propagation velocity (NZPV) decreases with increasing magnetic field. However, the declining trend of NZPVs slows down beyond 10 T. Moreover, for a constant transport current It, the Ic and Tcs decrease with the increasing magnetic field, which results in a simultaneous increase of NZPV with a decrease of MQE. [ABSTRACT FROM AUTHOR]

Controlling wave propagation pattern within acoustic fluid domains has been the motivation for the acoustic metamaterials developments to target applications ranging from acoustic cloaking to passive noise control techniques. Currently, various numerical and analytical approaches exist to predict the fluid domain material properties necessary for specific propagation pattern. Physical attempts to realize such material properties have revealed engineered material constructions that are focused on predefined wave propagation patterns. In the current paper, coupled fluid-structure one-dimensional metamaterial cell, in which piezoelectric active ingredient has been introduced, is manufactured to achieve controllable dynamic density. The density-controllable cell has been manufactured by coupling a water-filled cavity with piezoelectric elements in a cell of 4.5 cm length and 4.1 cm diameter subject to impulse excitation. A finite element model of the cell has been developed and its predictions are validated against the experimental results. The validated model is utilized to predict the changes in the pressure gradient inside the developed cell which is a direct measure of the changes introduced to the dynamic density of the acoustic metamaterial domain. With such predictions, it is demonstrated that densities as high as 3.2 gm/cm3 and as low as 0.72 gm/cm3 can be achieved experimentally for excitation frequencies ranging between 100 Hz and 500 Hz. [ABSTRACT FROM AUTHOR]

In this paper, we study the polarization states of the localized sagittal modes in a solid/solid one-dimensional phononic crystal with a defect layer. We have found that the well defined polarization of these modes, either transverse or longitudinal, for propagation in the direction of periodicity is completely modified for the case of oblique propagation. Thus for practical applications the polarization—the transverse/longitudinal component rate—of the defect modes will depend on the angle of incidence. For calculations, we use the supercell method; the criterion of energy balance is employed to determine the polarization state of all the acoustic waves. The results show the existence of localized elastic modes in the band gaps and resonant vibrations inside the allowed bands. By analyzing the amplitude profiles, we conclude that the displacement localization of both transverse and longitudinal components can be different. Consequently, the polarization of the transmission peaks could depend on the thickness of the sample. The interesting effect of change in polarization (from quasitransverse to quasilongitudinal) of some transmission peaks as function of the angle of incidence is reported. Calculations were made for an Epoxy/Sn superlattice with Zn as defect layer. [ABSTRACT FROM AUTHOR]

Based on an effective propagation constant and a frequency-dependent dielectric constant, the plane wave method is extended to calculate the complex photonic band diagram and the density of states for electromagnetic waves propagating in a two-dimensional finite structure with nonoverlapping dielectric cylinders of arbitrary radii, which may be randomly embedded in a dielectric matrix. The effective propagation constant is obtained by using the Twersky formula [J. Math. Phys. 3, 700 (1962)] and the scattering matrix method. A case study shows that an embedded defect with optimal radius in a finite photonic crystal can increase the first photonic band gap as compared to the similar structure without the defect. This work is expected to provide a useful tool in determining the photonic properties of a disorder dielectric medium with arbitrary embedded nanoparticles and nanowires. [ABSTRACT FROM AUTHOR]

Surface effect on the longitudinal and flexural wave propagation in straight nanofibers/nanowires is studied within the framework of continuum mechanics. Modified Euler-Bernoulli and Rayleigh-Love rod equations and modified Timoshenko beam equation were developed to take into account the surface effect. It was found that surface tension/stress plays appreciable influence on the wave propagation in nanofibers/nanowires at very small diameters. Wave dispersion relations were presented in closed form, and numerical calculations were performed to show the variation of the phase velocity with the wave number at varying surface property and fiber diameter. The given results can be used as the theoretical basis of dynamic characterization of nanofibers/nanowires and nanodevice design and analysis. [ABSTRACT FROM AUTHOR]

The debated question of the superluminal speed of information remains open to different interpretations in spite of recent, apparently conclusive, contributions. A different point of view is here considered, which is based on experimental results of microwave propagation experiments, in far-field conditions. They support the hypothesis of the existence of fast waves of the Zenneck type. [ABSTRACT FROM AUTHOR]

In this paper, the electrical characterization of semiconductor structure by acoustoelectric couplings (pressure-wave-propagation method) is theoretically studied and experimentally tested. Estimated signals for a Schottky diode structure fit very well the experimental measurements. Information on the screening length or on the voltage barrier can be directly obtained from the measurements. [ABSTRACT FROM AUTHOR]

A rigorous analysis of pulse propagation in planar photonic crystal (PhC) coupled cavity waveguides (CCWs) of finite length is reported. Conventional PhC waveguides, formed by a single line defect, are used at both interfaces of the CCW. An adiabatic taper based on progressively varying the radii of the spacing defects between cavities is used to achieve flat transmission bands with respect to the butt coupling case. The influence on the main parameters of the propagated pulse such as group delay, full width at half maximum and pulse attenuation are investigated for both the adiabatic and butt coupling cases. Furthermore, the Fabry-Perot formula has been used for modeling the pulse propagation along the CCW of finite length, which permits to analyze a large range of parameters avoiding the huge computation time requirements of finite-difference time-domain simulations. [ABSTRACT FROM AUTHOR]

Recently it was shown that the pressure wave propagation method, usually used to study electrical behavior of dielectric materials, can be applied to the nondestructive detection and quantitative analysis of adhesion defects in bilayer structures. In this paper, we investigate the possibilities open by the same method to detect and quantify adhesion defects in trilayer structures. After a brief recall of the principle of the method and of the main results obtained for bilayer structures, we describe the trilayer structures to be tested and present preliminary measurements of the acoustical and electrical properties of the materials constituting these samples. Measurements were carried out on kapton (52 μm)–adhesive (57 μm)–kapton (130 μm) and polyetheretherketone (PEEK) (138 μm)–adhesive (52 μm)–PEEK (138 μm) transparent samples. The signals are established and analyzed, with the help of simulations, in the cases of structures perfectly bonded, totally disbonded at one interface, and partially disbonded at one or at two interfaces. The excellent agreement between the measurements carried out on perfectly bonded and totally disbonded samples and simulations assesses the correctness of the signal expression for a multilayer structure. By analyzing the signals in the time domain, in a very simple manner, it is possible to determine at which interface the disbonds occur. In the case of partially disbonded structures at one interface, the value of the percentage of totally disbonded area in the tested zone determined by measurements or simulations is very close to that deduced from a photograph of the sample. If the transit time of the pressure pulse in each medium is larger than 11 ns measurements and simulations show that, owing to this method, it is possible to detect and localize in trilayer structures submicron gaps and a percentage of totally disbonded area as low as 10% in the tested zone, which is approximately equal to 30 mm2. In the case of partially disbonded samples at the two interfaces, it is possible to make a qualitative analysis of the measurements. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Starting with the scalar wave equation and relevant expressions for nonlinear dielectric constant of plasma, the propagation of a Gaussian ripple on a plane wave front of uniform intensity has been studied in the paraxial approximation. In the plane of the ripple width (along the y axis) and the ratio of the electric field intensities of the ripple and the main beam at r=0, z=0, (along the x axis) three distinct regions (for a given intensity of the main beam) can be identified which correspond to steady divergence, oscillatory divergence, and self-focusing of the ripple. The variation of the ripple width with distance of propagation has also been obtained for typical points in the three regions. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which demonstrated the surface wave propagation in a low-pressure collisional plasma column generated by the wave itself. Plasma column as a lossy inhomogeneous medium for surface wave propagation; Experimental procedure for measuring the dispersion diagrams; Experimental results and discussion; Conclusions.

Presents information on a study which examined the propagation of electromagnetic waves in media which are both conducting and dispersive using the one-dimensional telegraph equation. Model system; Numerical results; Physical applications; Discussions and conclusions.

Presents a study which examined the dynamic composite elastic medium theory which describes wave propagation at all frequencies. Details on the dynamic composite elastic medium theory; Numerical simulations used in the study.

Develops a theory which predicts the behavior of magnetostatic volume wave propagation in yttrium iron garnet films with the magnetic bias field applied at an arbitrary angle. Significance of electronically variable delay lines in microwave signal processing; Direction of magnetic wave propagation; Variation of internal angle and internal magnetic field with external field angle for an applied magnetic field.

Presents an analysis and experimental study of surface transverse wave (STW) resonators on quartz. Description of an STW propagation model; Structure of a cavity with a periodic discontinuity grating for guiding STWs; Definition of the transfer matrix for a periodic grating of metal strips.

Presents information on a study which evaluated tortuosity, the high-frequency limit of the squared propagation index, with narrow-band piezoelectric transducers on reticulated plastic foams. Methods; Results; Discussion.

Provides information on a study which analyzed reflection effects in oblique incidence grooved gratings in the presence of propagating surface acoustic waves. Methods; Results; Conclusion.

Describes a configuration of propagation of acoustic shear wave in Paratellurite off the [110] axis in the (001) plane. Information on acousto-optic interaction with reduced spreading of the slow shear acoustic wave in TeO[sub2]; Number of Bragg cells realized in order to validate the numerical results.

Focuses on a study which presented a technique, based on x-ray shadowgraphy, for visualization of the plasma jet propagation into the working fluid during their interaction in the reaction chamber. Experimental setup and procedure; Experimental results; Conclusions.

Presents a study which investigated the propagation of a directed pulse of electromagnetic radiation in a vacuum and in a rarefield, temporally dispersive medium. Vector potential in dispersive medium; Propagation in a vacuum; Conclusions.

Presents a study which examined frequency up-conversion of a high-power microwave pulse propagating in a self-generated plasma. Model equations for pulse propagation; Experimental methods; Comparison between experimental results and the theory.

Discusses the theoretically expected behavior of the mirage effect with the probe beam propagating through a transparent solid. Temperature distribution in the solid; Relation with refractive index gradients; Determination of the angle of deflection of the probe beam.

Presents a study that investigated Bleustein-Gulyaev piezoelectric surface-wave propagation under periodic metal-strip grating on piezoelectric cubic crystals. Formulation of the problem; Results; Discussion.

Reports on the dynamical properties of fluxon propagation in a discrete Josephson transmission line. Description of the discrete Josephson transmission lines (JTL) used in the circuit design; Illustration of the simplified equivalent circuit of the fabricated chip; Expression for the fluxon propagation velocity traveling in the continuous JTL by perturbation theory.

We report some experimental results of delay time in electromagnetic propagation in the presence of a lossy dielectric medium. The results were performed in the range of microwaves and showed a shortening of the delay time when the surface of the medium is situated very close to the wave path. A theoretical model dealing with surface waves of Zenneck type was considered. [ABSTRACT FROM AUTHOR]

Analyzes plane wave propagation at the composite-medium interface for the piezoceramic polymer composites with laminated periodic structure. Description of the composite structure; Solution to the field equations in the fluid region in the case of the fluid composite interface; Relationship used to evaluate the input acoustic impedance of a composite at the interface.

Discusses a study which examined the propagation and reflection properties of magnetoelastic waves in Fe[sub77.5]Si[sub7.5]B[sub15] amorphous wires. Condition in which the attenuation constant increases; Features of amorphous magnetic wires; Characteristics of the as-drawn wires; Action taken in order to realize the efficiency driving and pickup of the wave.

Presents a study which examined anomalous magnetoelastic waves in nickel wire. Demonstration of the anomalous propagation; Illustration of wave packets of positive and negative phase velocities; Phase and group delay changes due to transmitter motion.

Deals with a study wherein a general characteristic equation is derived in order to determine the propagating modes inside a circular waveguide with an impedance wall. Methods; Results; Discussion.

We experimentally demonstrate dramatically increased radiation from an 'invisible' source placed next to a sub-wavelength metal strip grating. The invisible source is a novel, highly reactive, array of antennas excited by a common feed, which weakly radiates in the far-zone. The metal grating used is sub-wavelength and non-resonant, which typically attenuates the overall radiation of a nearby source, especially in the transverse electric polarization. However, we show that such a grating screen with proper dimensions placed next to the 'invisible' source can in fact significantly enhance the radiated field strength, far beyond the free space radiation of this 'invisible' radiator, by an order of magnitude. This radiation enhancement is facilitated through the conversion of evanescent waves of the specially designed reactive source into propagating waves, and its level is inversely related to the source-grating distance. The physical phenomenon is shown in simulations and measurements at microwaves. This novel radiation enhancement effect is shown to have potential applications in various areas such as proximity sensing, detection, and measurement of distance. [ABSTRACT FROM AUTHOR]

The chirality of MgO-doped periodically poled lithium niobate (MgO:PPLN) by electro-optic effect was studied. It shows that optical propagation is reciprocal in MgO:PPLN under a transverse electric field and quasi-phase-matching condition, which bears similarity to natural optically active material like quartz. The specific rotation is shown to be proportional to the transverse electric field, making large polarization rotation in optically active material with small size possible. We also demonstrate that the chirality of MgO:PPLN can be controlled by the external electric field. [ABSTRACT FROM AUTHOR]

In exchange coupled granular films the reversal process is usually that of reverse domain nucleation and domain wall propagation. Local effects such as surface irregularities can affect the nucleation process significantly. We describe the effects of nucleation arising from both sample shape effects and the process used to cut the samples. Cutting techniques such as the use of ultrasonic cutters lead to a large increase in nucleation, which distorts the hysteresis loop. Deposition through masks causes shadowing effects at the edges that also distort the loops. Cutting with a diamond scribe appears to give the best outcome. Implications for devices based on nanoelements are discussed. [ABSTRACT FROM AUTHOR]